Coffee water calculator
Water needed is the coffee dose times the ratio. Twenty grams at 1:16 takes 320 g of water, which brews to about 280 ml in the cup once the grounds have taken their share.
How to work out brew water
Water quality matters nearly as much as the quantity. Very soft or distilled water extracts poorly and produces flat, hollow coffee, because minerals participate in extraction. Very hard water over-extracts bitter compounds and scales the kettle. A moderate mineral content; roughly 75 to 150 ppm total dissolved solids: is the range specialty brewing standards aim for, which is why some cafés filter and then deliberately remineralise.
Questions
320 g at 1:16, or 300 g at 1:15 for something stronger.
Near enough: one millilitre of water weighs one gram at room temperature.
Considerably. Distilled water extracts poorly; very hard water over-extracts. Around 75–150 ppm is the target range.
Between 90 and 96 °C for most filter methods. Off the boil for thirty seconds is close enough.
The grounds retain about two grams per gram of coffee. Twenty grams of coffee keeps roughly 40 ml.